The Pentagon insisted Tuesday that there is "no mission creep” in Iraq despite the rising number of U.S. troops in the embattled country with more on the way.

Rear Adm. John Kirby, the Pentagon press secretary, confirmed that 650 American troops were on the ground in Iraq, all of them dispatched by President Barack Obama since June 16.

Two hundred U.S. troops sent Monday, including 100 previously staged in Kuwait, were accompanied by Army Apache attack helicopters to be based at the Baghdad airport.

Kirby said Sunni Islamic militants who’ve seized large sections of the country since June 10 pose a threat to Baghdad but are meeting stiffened resistance from Iraqi security forces aided by Shiite militiamen.

“It continues to be very dangerous,” Kirby told reporters at the Pentagon. “The threat continues to be very real. But we have seen Iraqi security forces in and around Baghdad begin to reinforce themselves and prepare to defend, and they are taking the offensive. And we saw this over the weekend up near Tikrit (north of Baghdad). So it’s a contested environment right now.”

With Obama authorized under the War Powers Act to send up to 770 total troops to Iraq, or 120 more than are now there, reporters pressed Kirby on whether that number is a ceiling or could go still higher.

Kirby provided somewhat mixed responses.

The admiral said the 770 authorized troops should be enough to accomplish two stated missions: protect the U.S. Embassy and the Baghdad airport, which has been used in recent weeks to move some of the embassy’s 5,300 employees; and assess the current security situation and the capabilities of Iraqi security forces.

At the same time, Kirby said that Obama must have the flexibility to make the best decisions to preserve U.S. interests in and around Iraq.

“Is there a grand total (of troops)? No. But in terms of the grand total limit, he’s the commander in chief. He makes these decisions. And he needs the freedom to make those decisions as he and the military commanders and the civilian leadership here in the Pentagon advise him to.”

Kirby denied, however, that the United States is being inexorably pulled back into a war from which Obama withdrew the last U.S. combat brigades at the end of 2011.

“There's no mission creep,” Kirby said. “The missions haven't changed. Some of the numbers have been added in the security assistance realm. And, look, it’s very fluid. And the commander in chief and the military leadership here in the building, I think, expect and should have a certain measure of flexibility here in how we manage the resources available.”

Even as reporters asked whether U.S. involvement in Iraq is escalating, Baghdad’s envoy to Washington said American delay in delivering promised weapons is forcing the Iraqi government to turn to Iran, Russia and Syria for help.

“Time is not on our side,” Ambassador Lukman Faily said at the Carnegie Endowment for International Peace in Washington. “Further delay only benefits the terrorists.”

The fledgling Iraqi air force announced Sunday that Russia was sending five SU-25 jet fighters to Iraq to help the government repulse attacks by the rebels called the Islamic State of Iraq and Syria.

The group announced Sunday it was changing its name simply to Islamic State and declared the creation of a caliphate stretching from Diyala, Iraq, near the Iran border to the east to Aleppo, Syria, not far from Turkey to the north and east.

“What they call themselves is up to them," Kirby said Tuesday. "I understand they've declared this caliphate. But declaring something doesn't make it so.”

Kirby said there’s been no delay in the delivery of 36 F-16 fighter jets to Iraq, saying they are on course to arrive on schedule this fall.

Yet he acknowledged that the recent removal of American contractors from Joint Base Balad, headquarters of the Iraqi air force, could complicate delivery of the American jets.

“We had to move some contractors out -- or, actually, the company had to move contractors out of Balad, contractors that were there to help prepare for the arrival of those aircraft,” Kirby said. “They are no longer working there at Balad. So that could have an impact on eventual delivery.”

Iraq is a sovereign nation, Kirby said, and the United States cannot control which other governments it reaches out to for help.

While insisting that the United States has no plans to collaborate with Iran, Kirby said reporters asking about Iranian troops’ presence in Iraq to bolster government forces “presumes that we’re in open conflict with Iran.”